U.S. Pat. No. 4,383,172 granted May 10, 1983 discloses an apparatus for measuring coating thicknesses on continuously moving material, the apparatus utilizing beta backscatter techniques which requires that a probe be placed into contact with the strip of continuously moving material.
U.S. Pat. No. 4,451,732 issued May 29, 1984 discloses an apparatus similar to the prior patent but which has the capability of measuring the coating thickness on a continuously moving strip of material wherein the coating is deposited upon an angularly disposed portion of the strip of material.
It is also commercially known to measure the thickness of a coating on a piece of material utilizing X-ray technology. By utilizing X-ray technology, it is not necessary to contact the coating on the material. However, it is necessary that the X-ray unit be disposed a precise distance away from the surface of the coating to be measured.